Submitted to: Fungal Genetics and Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/2/2006
Publication Date: 4/1/2007
Citation: Harris, L., Alexander, N.J., Saparno, A., Blackwell, B., Mc Cormick, S.P., Desjardins, A.E., Robert, L., Tinker, N., Hattori, J., Piche, C., Schernthaner, J., Watson, R., Ouellet, T. 2007. A novel gene cluster in Fusarium graminearum contains a gene that contributes to butenolide synthesis. Fungal Genetics and Biology. 44(4):293-306. Interpretive Summary: Cattle grazing on tall fescue grass that is infected with the mold Fusarium graminearum can become afflicted with a disease called fescue foot. This disease can lead to gangrene of the affected area and ultimately lead to the death of the animal. The causal agent of fescue foot has not been determined but it is believed that a toxin made by F. graminearum, butenolide, may be involved. By using gene libraries of the mold, we identified genes that were expressed during infection of plant material. We then made knockout mutants that can no longer make butenolide. This is the first report of the identification of a gene involved in the biosynthetic pathway of butenolide. A better understanding of the genes involved in butenolide production may lead to novel strategies for reducing or eliminating these mycotoxins.
Technical Abstract: The development of expressed sequence tag (EST) databases, directed transformation and a sequenced genome has facilitated the functional analysis of Fusarium graminearum genes. Extensive analysis of 10,160 ESTs, derived from13 cDNA libraries of F. graminearum grown under diverse conditions, identified a novel cluster of eight genes (gene loci fg08077 – fg08084) located within a 17 kb region of genomic sequence contig 1.324. The expression of these genes is coordinately up-regulated under growth conditions that promote mycotoxin production. Gene disruption and add-back experiments followed by metabolite analysis of the transformants indicated that one of the genes, fg08079, is involved in butenolide synthesis. Produced by several Fusarium species, the mycotoxin butenolide has been suggested but not proven to be associated with tall fescue toxicoses in grazing cattle. This is the first report of the identification of a gene involved in the biosynthetic pathway of butenolide.